1. Field of the Invention
The invention relates to the storage of fluids which have potential for polluting the environment. In particular, the invention relates to means for accessibly storing such fluids in an underground storage tank such that regular inspection and maintenance of the storage tank may take place and having means for preventing any fluid leakage from the tank from entering the environment.
2. Prior Art
The invention is directed to the safe storage of liquids which if loosed into the environment could pollute and possibly produce toxic effects. Insight into the problem was first garnered from investigations of present day methods for storing gasoline at automobile service stations. The gasoline storage tanks at these stations are buried underground. In the emplacement of these storage tanks, an excavation is made in the earth and a bed of gravel is laid down. The storage tank is emplaced upon the bed of gravel and additional gravel is placed about it to support it and the weight of the gasoline which it will store. Piping to convey gasoline to and from the tank is buried as well. There is, of course, an injection port, accessible from above ground, into which the gasoline fuel is injected in filling the tank.
So stored, the gasoline storage tank is subject to the deterioration both from without and within. Water accumulating within the gasoline storage tank along its lower-most surfaces tends to rust the tank from the inside. Environmentally derived liquids attack the tank from without. Often, sooner than expected, the storage tank may spring a leak. The leak may initially be so small as to prove unnoticeable, yet gasoline is leaking into the ground and finding its way into ground water flow and aquifers. In the past, when such leakage was discerned, it was often allowed to continue. Such decisions were predicated upon the high cost of excavating the gasoline storage tanks and replacing them.
In U.S. Pat. Nos. 4,682,911 and 4,778,318 issued to J. Moreland, the use of a plastic membrane to form a catch basin into which spilled or leaking gasoline will accumulate and from which the accumulated gasoline may be withdrawn is disclosed. In the '911 patent, Moreland makes an excavation for the gasoline storage tanks in a manner similar to that done in the prior art. The excavation is then lined with a membrane and the membrane-lined excavation is partially filled with gravel to form the base for the tank. As before, more gravel is provided until the tank is totally surrounded by this material. Moreland, in his disclosure, notes that the membrane is subject to pinhole damage. Thus, gasoline leaking from the tank can find its way past the membrane and into the earth and the water systems therein. This would be especially true if pinhole damage occurred at the lower-most regions of the membrane lined excavation. In addition, a ruptured storage tank, even though surrounded by Moreland's membrane, must still be dug up in order to be replaced. Such excavation procedures are singularly expensive.
It is an object of the present invention that liquid storage tanks, for example, gasoline storage tanks, will remain readily accessible for inspection and maintenance even though emplaced beneath the ground surface. It is further desired of the invention that the need for expensive excavation in order to replace a damaged storage tank will be obviated. In addition to accessibility for visual and tactile inspection techniques, the invention has as an objective the use of sensors to detect abnormal conditions as well as providing the means for assisting in the extinguishing of fires fed by the fluids stored within the tank or adjacent combustible materials.